Superplastic forming and diffusion bonding (SPF/DB) may be used to form monolithic metal structures having complex shapes and deep drawn features. For example, SPF/DB may be used to form exterior assemblies of aircraft.
Structures formed by SPF/DB may exhibit “surface mark-off.” Surface mark-off is a marring of the surface of the formed structure. It may appear as a crease or other surface defect that interrupts the smoothness of the surface. Surface mark-off can not only be cosmetically unsightly, but can have other consequences. For instance, surface mark off on the outer-surface of an exterior aircraft assembly may increase aerodynamic drag.
It would be desirable to suppress surface mark-off in SPF/DB structures.